The reduction in solar ultraviolet radiation in the declining phase of the 11-year solar cycle nudges the climate in the Northern Hemisphere towards colder winters in northern Europe and the United States reports a study online this week in Nature Geoscience. If the amplitude in solar ultraviolet radiation over the cycle is four to six times larger than previously thought — as inferred from the most recent satellite measurements — foreseeable changes in solar UV radiation could help with decadal climate prediction.

Sarah Ineson and colleagues estimated the difference in solar UV radiation between solar maximum and solar minimum from satellite measurements taken between 2004 and 2007. They used these estimates to simulate the climatic response to changes in solar UV radiation of this magnitude with a climate model. The simulations suggest that during solar minimum, Northern Hemisphere climate is pushed towards a state of mild winters in Canada and southern Europe and cold winters in northern Europe and the US, which is consistent with the winter weather experienced around the Atlantic between 2009 and 2011 when solar activity was low.

In an accompanying News & Views article, Katja Matthes writes “The study by Ineson and colleagues hints at a strong effect of the 11-year solar cycle on decadal surface climate during Northern Hemisphere winter. But the findings await confirmation of the large amplitude of variability in solar ultraviolet radiation with SIM [Spectral Irradiance Monitor] measurements taken over a longer period”.